Rotary abrasive tool

ABSTRACT

A rotary abrasive tool employs a spiral-wound abrasive strip having successive wraps bonded together at least at one end by an adhesive to form a tube of generally cylindrical shape. A short driver is fixed by adhesive at one end of the tube and a portion thereof may project a short distance into the tube. The tube may also comprise a plurality of short length tubular segments having adhesive material on each end face and bonded together end-toend. The hollow center of the tube may be filled with friable material bonded to the inner surface of the tube to provide an abrasive core, and also to provide the inner wrap of the tube with self-trimming capability when the tube is rotated in oblique frontal contact with a work piece.

States atent [1 1 finite Ewell 1 May 8, 1973 [54] ROTARY ABRASIVE TOOL [22] Filed: June 30, 1971 [21] Appl. No.: 158,419

[76] Inventor:

Related US. Application Data [63] Continuation-impart of Ser. No. 68,407, Aug. 31,

1970, abandoned.

UNITED STATES PATENTS 1,119,760 12/1914 Koontz ..51/403 2,358,724 9/1944 Manchesterm. ....5l/403 2,290,098 7/1942 Field ..51/297 2,458,362 l/l949 Field 51/403 2,309,456 1/1943 Hoskin ..51/403 736,114 8/1903 Koenig ..51/403 2,038,782 4/1936 Ellis .i..5l/297 691,066 l/l902 Miller ..5l/403 3,364,630 1/1968 Rusk ..5l/298 X Primary Examiner-Donald G. Kelly Att0rneyLyon & Lyon [57] ABSTRACT A rotary abrasive tool employs a spiral-wound abrasive strip having successive wraps bonded together at least at one end by an adhesive to form a tube of generally cylindrical shape. A short driver is fixed by adhesive at one end of the tube and a portion thereof may project a short distance into the tube. The tube may also comprise a plurality of short length tubular segments having adhesive material on each end face and bonded together end-to-end. The hollow center of the tube may be filled with friable material bonded to the inner surface of the tube to provide an abrasive core, and also to provide the inner wrap of the tube with self-trimming capability when the tube is rotated in oblique frontal contact with a work piece.

15 Claims, 12 Drawing Figures Patented May 8, 1973 3,731,437

2 Sheets-Sheet 2 Em J2 INV ENTOR J056PH ,8 (FM/6&4

A TTOZA/(FVS ROTY ABIVE TL This application is a continuation-in-part of my copending application for Abrasive Tool, Ser. No. 68,407 filed Aug. 3 l 1970 now abandoned.

This invention relates to a rotary abrasive tool of the type employing a spiral-wound abrasive strip. Conventional cartridge rolls are formed in this fashion, using an abrasive belt wound on a construction mandrel and provided with a central opening. This opening later receives a separate removable drive element such as, for example, a one-piece drive shaft tightly fitting the central opening and having a shaft extension engaged by the chuck or collet of a power drive.

For many purposes, the conventional cartridge roll is an excellent substitute for the rotary grinding wheel. While not comparable to the grinding wheel in precise machine-mounted operations, or in very heavy snagging tasks such as are encountered in a foundry, the cartridge roll has been accepted for many deburring and polishing operations. For effective use, however, the cartridge roll must be rotated at high peripheral speeds, often in the range of 3,000-7,000 surface feet per minute. This translates to rotational speeds of 15,000 to 35,000 RPM. This in turn demands rigid axial alignment to minimize vibration. This required alignment of the cartridge roll is achieved by and is dependent upon the substantially full insertion of the closely fitted removable metallic drive element. However, the presence of this drive element near the forward end of the cartridge roll limits the oblique or frontal use of the cartridge roll because the latter may be worn only until the forward end of the metallic drive element is exposed to contact with the work piece. At this point, frontal use must be discontinued until the drive element is removed, and a shorter one compatible with the shortened cartidge roll is installed. Still shorter drive elements must be substituted as the cartridge roll successively wears to a minimum acceptable axial dimension.

A second limiting factor in the use of the conventional cartridge roll is the inherent tendency of the innermost wrap to fray in an uncontrolled fashion and to extend into an irregular unsightly collar, even in high speed use. In practice, the operator frequently interrupts his work to tear away the offending extended fabric. This innermost wrap is the only one without a next successive underlayer to support its contact with the work piece. Without such support, and with its stiff adhesive coating progressively worn away as the outer layers of the roll are abraded in oblique frontal contact with a work piece, the innermost wrap degenerates to its original form as a relatively soft woven fabric.

Also, conventional cartridge rolls suffer decreasing rigidity in axial alignment support as the forward portion of the spiral wrap is abraded and thinned by use. As this thinning progresses, the once-tight fit between the drive member and the abrasive wrap begins to loosen, with the result that the cartridge roll is discarded long before its available abrasive material has been usefully employed. The operator discards the partially used abrasive cartridge roll rather than to risk an accidental and possible hazardous displacement during high speed use.

Furthermore, the conventional cartridge roll frequently has its useful life shortened or abruptly terminated by an inadvertent tear of the abrasive strip at some point forward of the circumferentially bonded area adjacent the rear end of the tube. This tear can be caused by a projection of the work piece, or by an inadvertent or careless handling of the tool. In any event, a cut through the outer layer of the spiral-wound strip allows the portion of the strip located forward of the cut to flare outwardly under centrifugal force. Since the rotation speed is very high, a tear often develops before the operator is aware it is happening. A total rip-off frequently occurs before the motor can be stopped. Depending on where the cut occurred, the tool is damaged and its service life reduced to the extent of the material lost.

It is an important object of the present invention to eliminate or minimize the foregoing shortcomings of the conventional cartridge roll, and to provide a superior rotary abrasive tool in which contact between the work piece and the drive element is avoided, until the abrasive element is substantially consumed, and wherein the objectionable irregular collar is prevented from forming when the tool is rotated in oblique frontal contact with a work piece. It is also an important object of the present invention to provide a superior rotary abrasive tool in which rigid support of the abrasive tube is maintained throughout the useful life of the tool. Another important object is to provide such an improved tool which is constructed to minimize damage in the event a tear should develop in the outer periphery of the tool. These objects are achieved in a construction in which a short stub driver is tightly and permanently bonded coaxially to the interior of the spiral-wound abrasive strip, and wherein a liner of friable material is bonded to the remaining length of the inner surface of said strip. The friable liner provides an abrasive core and also supports the innermost wrap of the spiral-wound abrasive strip, and causes this inner wrap to be trimmed off automatically as the tool is rotated in oblique frontal contact with a work piece. A metallic or non-metallic flange fixed to the driver may be adhesively bonded to an end face of the abrasive tube to prevent any looseness from developing between them during the life of the tool. The abrasive tube may be formed of two or more individual spirally wrapped coaxial members adhesively bonded end to end, and with a coating of adhesive on the end faces, so that a tear developing in one section cannot progress to the next. Of equal importance, the progress of a tear developing in any one section is immediately inhibited by l the lesser width involved, thus reducing the centrifugal force exerted, and/or by (2) the support provided by the closely adjacent bonded surfaces.

Other and more detailed objects and advantages will appear hereinafter.

In the drawings:

FIG. 1 is a side elevation showing a preferred embodiment of this invention.

FIG. 2 is an axial sectional view.

FIG. 3 is a transverse sectional view taken substantially on the lines 3-3 as shown in FIG. 2.

FIG. 4 is an axial sectional view showing a modification.

MG. 5 is a transverse sectional view taken substantially on the lines 5-5 as shown in FIG. 4.

FIG. 6 is an axial sectional view showing the abrasive tool being rotated in oblique frontal contact with a work piece.

FIG. 7 is a side elevation showing a modified form of this invention.

FIG. 8 is a longitudinal sectional view of the device of FIG. 7.

FIG. 9 is a view similar to FIG. 8 showing a modified form of driver.

FIG. 10 shows the device of FIGS. 7 and 8 in oblique frontal contact with a work piece.

FIG. 11 is a side elevation showing another modified form of this invention.

FIG. 12 is a longitudinal sectional view of the device of FIG. 1 1.

Referring to the drawings, the rotary abrasive tool generally designated 10 comprises a spiral-wound abrasive strip 11 forming a tube 12 having a substantially cylindrical outer surface 13 and a concentric central opening 14. The strip 11 is formed of acloth backing having abrasive grit bonded thereto by a suitable adhesive. The successive wraps of the strip are joined by a narrow spiraling bond of adhesive 15 near one end of the tube 12. A friable resilient central support or liner 17 fills the central opening 14 and is adhesively attached to the inner surface of the innermost wrap of the abrasive strip 11. In the device shown in FIGS. 1, 2, 3 and 6 of the drawings, the liner .17 is composed of plastic foam.

A stubdriver or stub shaft 19 projects for a short distance into the central opening 14 in the tube 12 and is provided with an internally threaded socket 20 for axial reception of a threaded drive shaft projecting from the high speed motor 21. The stub driver extends into the tube 12 for a distance less than one-half of the full length of theopening 14. In practice, the abrasive strip 1 1 is tightly wound, not on a mandrel, but directly on adhesive material 15 covering the inserted portion of the stubdriver 19, with the adhesive material continuingbetween successive wraps. The stub driver 19 is thus adhesively bonded to the innermost wrap of the abrasive strip. 11 and comprises a permanent integral part .of the assembly constituting the rotary abrasive tool 10. A slot 22in the stub' driver 19 receives a portion of the inner end 23 of the abrasive strip 11 and adhesive 15 to assist in providing the solid bonded connection between the stub driver 19 and the tube 12. An axial construction hole 24 extending through the liner 17 and stub driver 19 may be provided, if desired, for purposes of fabrication. Bonded in place, the relatively short stub driver joins with the wrapped abrasive strip to form a cantilever capable of maintaining fixed axial alignment of the whole under the high speed and severe operating conditions of normal use.

In operation, as shown'in FIG. 6, the rotary abrasive tool 10 is rotated by the high speed motor 21 in oblique frontal contactwith a work piece 25- for smoothing the work piece and removing burrs 26 therefrom. Wearing away of the tube 12 and liner 17 at the forward end produces a conical wear surface 27. Without the support of the liner 17 at the extreme innerend 28.0f the wear surface 27, a loose projection or collar would be formed by the innermost wrap of the abrasive strip 11, which collar would project forward of the small end 28 and interfere with action of the tool. The liner 17 supports the innermost wrap and prevents such a collar from forming, and the liner wears away by contact with the work piece 25 and without damage to the work piece 25. The wearing action on the surface 27 and liner l7 continues until substantially the full length of the tube 12 has been consumed; when the wear surface 27 approaches the projecting end of the driver 19, a brief side-wise use is all that remains. Essentially the full length of the tube 12 formed by the spiral-wound abrasive strip 1 1 is thus consumed without interference by the driver.

From the foregoing description, it will be understood that the backup support afforded by the presence of the friable liner 17 provides the innermost wrap of the abrasive strip with self-trimming capability, and the short stub driver insures that essentially the full length of the abrasive strip tube may be usefully employed.

In the modified form of the invention shown in FIGS. 4 and 5, the tube 120 is constructed in the same manner previously described, but the liner 170 comprises a thin tubular element formed of non-metallic friable material adhesively bonded to the innermost wrap of the abrasive strip 11a. In practice, this tubular element may be formed by a coating of liquid or paste containing the adhesive material, semi-cured before initiating the wrapping process on the stub shaft-The stub driver 19a comprises a cylindrical member encircled by a nonmetallic bushing 30 and bonded thereto. The bushing 30 projects for a limited distance into the central opening 14a of the tube 12a and is adhesively bonded thereto. The stub driver 19a is provided with an axially extending spindle 31 for reception by the chuck or collet of the high speed motor 21a. A slot 22a in the stub driver 19a and bushing 30 receives the innermost end of the abrasive strip 23a in the manner previously described. The operation of the device shown in FIGS. 4 and 5 is the same as that described above.

. Itwill be understood that either form of driver, 19 or 19a, may be used with either form of liner, 17 or 17a. In the modified form of this invention shown in FIGS. 7-10, the spirally wrapped abrasive tube 50 has a driver 51 provided with an end flange 52. The driver is positransmitting the driving force imparted by the high I speed power tool 55. The forward and. un-glued portion of the abrasive wrap, in the tube 50, has been found to be self-supporting except the innermost wrap, under the stress of high speed abrasive use, in both frontal and side-wise applications. The innermost wrap is supported by friable filler material forming a central core 56 in the center of the tube 50; The innermost wrap is thus separately supported and caused to beselftrimming in abrasive contact withthe work piece.

It will be understood that the structural stability of the present invention is no way dependent on full insertion of a drive member, as is the case with a conventional cartridge roll. On the contrary, the rear face drive mounting of this form of the invention insures for the first time that essentially the full length of the abrasive tube 50 may be usefully employed in frontal or side-wise use, as may be desired. In addition, the wear or abrasion of the forward end of the abrasive wrap in no way affects the axial stability of the device. Further, the innermost wrap is prevented from extending into an unsightly frayed collar by the presence of back-up material which acts to trim the wrap neatly in abrasive contact with the work piece. Finally, the center opening filled with bonded-in-place abrasive grain mix furnishes not only support for the innermost wrap but adds a new abrasive contribution in contact with the work piece, as shown in FIG. 10. The layer of adhesive material 57 which bonds the surface of the end flange 52 to the end face 53 of the tube 50 joins with the spirally positioned layer 54 of adhesive material to form an unusually strong and dependable bond, with the spiral edge of the wraps each individually encompassed by the adhesive which bonds to the flange 52.

The driver 58 shown in FIG. 9 has an end surface 60 bonded by adhesive material 61 to the end face of the abrasive tube 62 in the same manner described in connection with FIGS. 7 and 8. The drivers 51 and 58 may be provided with a short central axial projection 63 and 64 which is useful in insuring precise concentricity between the driver and the abrasive tube. It is important that the rotary axes of the driver and the abrasive tube be coincident and that the flange surfaces 57 and 60 be perpendicular to those axes.

In the modified form of the invention shown in FIGS. 11 and 12, the abrasive tube 70 is formed of a plurality of individual spirally wrapped tubular segments 71, 72 and 73, which may be duplicates. Adjacent end faces 74 and 75, as well as exposed end faces 76 and 77, are each coated with adhesive material. Capillary action draws this adhesive material between the layers of the spirally wrapped segments near the ends thereof, creating a spiral circumferential bond of very short axial length but of considerable strength. The drive shaft 78 is bonded within theinterior of the segment 73. Friable filler back-up material forms a core 79 extending from the drive shaft 78 through the central opening in the remainder of the composite abrasive tube 70 and provides self-trimming capability for the innermost wrap of the segments 71, 72. In this structure, an inadvertent cut at any point along the length of the abrasive tube 70 may cause the abrasive strip to tear adjacent the cut, but the damage is limited in width by the isolation of one bonded section to the next. A tear developing in the outer surface of any segment is immediately inhibited by the lesser width involved which reduces the magnitude of centrifugal force exerted and by the support provided by the closely adjacent circumferential bonds. In operation, a tear is quickly snuffed out by these built-in retardant means.

Having fully described my invention, it is to be understood that I am not to be limited to the details herein set forth but that my invention is of the full scope of the appended claims.

I claim:

1. A rotary abrasive tool comprising, in combination: a spiral-wound abrasive strip forming a tube, adhesive material at one end of the tube bonding successive wraps together, a metallic driver adhesively bonded to the same end of the tube and projecting coaxially away from the tube, said driver and adhesive bond providing the tube with a structurally competent power drive means for high speed rotation, a liner of friable material bonded to the inner surface of the tube and extending from the driver to the other end of the tube, said liner providing the inner wrap of the tube with selftrimming capability, when the tube is rotated in oblique frontal contact with a work piece.

2. The device set forth in claim 1 in which said driver is provided with an internally threaded drive socket.

3. The device set forth in claim 1 in which said driver includes an axially projecting stem.

4. The device set forth in claim 1 in which a portion of the driver projects into the interior of the tube.

5. The device set forth in claim 1 in which a portion of the driver projects into the interior of the tube and is encircled by a non-metallic bushing.

6. A rotary abrasive tool comprising, in combination: a tube comprising a spiral-wound abrasive strip having successive wraps bonded together by an adhesive, a coaxial stub driver projecting into one end of the tube and fixed thereto, and a liner of friable material bonded to the inner surface of the tube and extending from the driver to the other end of the tube, said liner providing the inner wrap of the tube with self-trimming capability, when the tube is rotated in oblique frontal contact with a work piece.

7. The device set forth in claim 6 in which said liner comprises a foam member substantially filling the interior of the tube.

8. The device set forth in claim 6 in which said liner comprises a thin annular friable layer.

9. The device set forth in claim 6 in which said liner comprises friable abrasive material filling the interior of the tube to provide an abrasive core.

10. A rotary abrasive tool comprising, in combination: a spiral-wound abrasive strip forming a tube having an end surface, adhesive material between successive wraps near said end surface of the tube bonding said wraps together, a driver having an end face adhesively bonded to said end surface of the tube, said driver and said adhesive bond providing the tube with a structurally competent power drive means for high speed rotation, the interior of the tube being filled with friable abrasive material to provide an abrasive core.

11. The combination set forth in claim 10 in which said driver comprises a stub shaft having a flange, the said end face being provided on said flange.

12. The combination set forth in claim 10 in which said driver includes an internally threaded drive socket.

13. The combination set forth in claim 10 in which the driver has a short projection extending into said tube to insure concentricity.

14. A rotary abrasive tool comprising, in combination: spiral-wound abrasive strips forming a plurality of tube segments each having end faces, adhesive material covering each end face and encompassing the spiral edges of the abrasive strips and extending between successive wraps by capillary action, said adhesive material bonding said tube segments in end-to-end coaxial relationship to form a tube and forming axially spaced stiflened zones along the length of the tube, and a driver projecting into and adhesively bonded to only one tube segment at one end of said tube.

15. The combination set forth in claim 14 in which friable abrasive material fills the interior of the other tube segments to provide an abrasive core. 

1. A rotary abrasive tool comprising, in combination: a spiralwound abrasive strip forming a tube, adhesive material at one end of the tube bonding successive wraps together, a metallic driver adhesively bonded to the same end of the tube and projecting coaxially away from the tube, said driver and adhesive bond providing the tube with a structurally competent power drive means for high speed rotation, a liner of friable material bonded to the inner surface of the tube and extending from the driver to the other end of the tube, said liner providing the inner wrap of the tube with self-trimming capability, when the tube is rotated in oblique frontal contact with a work piece.
 2. The device set forth in claim 1 in which said driver is provided with an internally threaded drive socket.
 3. The device set forth in claim 1 in which said driver includes an axially projecting stem.
 4. The device set forth in claim 1 in which a portion of the driver projects into the interior of the tube.
 5. The device set forth in claim 1 in which a portion of the driver projects into the interior of the tube and is encircled by a non-metallic bushing.
 6. A rotary abrasive tool comprising, in combination: a tube comprising a spiral-wound abrasive strip having successive wraps bonded together by an adhesive, a coaxial stub driver projecting into one end of the tube and fixed thereto, and a liner of friable material bonded to the inner surface of the tube and extending from the driver to the other end of the tube, said liner providing the inner wrap of the tube with self-trimming capability, when the tube is rotated in oblique frontal contact with a work piece.
 7. The device set forth in claim 6 in which said liner comprises a foam member substantially filling the interior of the tube.
 8. The device set forth in claim 6 in which said liner comprises a thin annular friabLe layer.
 9. The device set forth in claim 6 in which said liner comprises friable abrasive material filling the interior of the tube to provide an abrasive core.
 10. A rotary abrasive tool comprising, in combination: a spiral-wound abrasive strip forming a tube having an end surface, adhesive material between successive wraps near said end surface of the tube bonding said wraps together, a driver having an end face adhesively bonded to said end surface of the tube, said driver and said adhesive bond providing the tube with a structurally competent power drive means for high speed rotation, the interior of the tube being filled with friable abrasive material to provide an abrasive core.
 11. The combination set forth in claim 10 in which said driver comprises a stub shaft having a flange, the said end face being provided on said flange.
 12. The combination set forth in claim 10 in which said driver includes an internally threaded drive socket.
 13. The combination set forth in claim 10 in which the driver has a short projection extending into said tube to insure concentricity.
 14. A rotary abrasive tool comprising, in combination: spiral-wound abrasive strips forming a plurality of tube segments each having end faces, adhesive material covering each end face and encompassing the spiral edges of the abrasive strips and extending between successive wraps by capillary action, said adhesive material bonding said tube segments in end-to-end coaxial relationship to form a tube and forming axially spaced stiffened zones along the length of the tube, and a driver projecting into and adhesively bonded to only one tube segment at one end of said tube.
 15. The combination set forth in claim 14 in which friable abrasive material fills the interior of the other tube segments to provide an abrasive core. 